Problems with logic trees in earthquake hazard evaluation

Logic trees make sense when used in earthquake risk analysis where costs are compared for specific outcomes. However logic trees fail in earthquake hazard analysis when they are used to develop earthquake ground motions for applications in engineering. The failure stems from a misguided attempt to assign numbers for degrees of belief which are personal and indefinable, almost like love or taste, and for which there are neither tests nor measurements. The result is a complicated jumble of egocentric impressions. In contrast, the need in engineering is to have values that are based as much as possible on evidence.